Transcriptome Screening of Hormone-Regulated Genes Related to Fruit Development in Zizyphus jujuba Mill. cv. Goutou Fruits at Different Ripening Stages

<i>Zizyphus jujuba</i> Mill. cv. Goutou is an edible and medicinal fruit whose development significantly impacts the metabolism and accumulation of nutrients and is regulated by plant hormones. In this study, the metal element and triterpene acid content were investigated and transcriptomic analyses were conducted to evaluate changes in seven ripening stages (Stages I-VII) of <i>Z. jujuba</i> Mill. cv. Goutou. We first analyzed seven metal elements and found that the concentrations of Magnesium (Mg), Aluminum (Al), Calcium (Ca), Manganese (Mn), and Cuprum (Cu) were highest at Stage I; in comparison, the concentrations of Zinc (Zn) and Ferrum (Fe) were highest at Stage IV. Additionally, three triterpene acids were detected in the fruits, with the contents of betulinic acid and oleanolic acid being highest at Stage VII and that of ursolic acid being highest at Stage I. Subsequently, through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, we identified 40, 18, 9, 6, and 11 differentially expressed genes involved in the auxin, abscisic acid (ABA), ethylene, gibberellic acid (GA), and jasmonic acid (JA) signaling pathways, respectively. Notably, genes associated with ABA, including <i>ZjABA3</i>, <i>ZjABA4</i>, <i>ZjABA6</i>, <i>ZjABA7</i>, <i>ZjABA10</i>, <i>ZjABA11</i>, <i>ZjABA15-ZjABA19</i>, <i>ZjABA22-ZjABA25</i>, and <i>ZjABA27-ZjABA33</i>, were downregulated from Stage I to Stage VII. Conversely, the expression of <i>ZjACO</i> in the ethylene signaling pathway was the highest at Stage VII. <i>ZjMYC2-1</i>, a JA signaling pathway gene, was significantly induced at Stage I compared to in the other stages. The genes <i>ZjGID-1</i> and <i>ZjTF-1</i>, related to GA, exhibited the highest expression levels at Stage VI.